1. Field of the Invention
The present invention relates generally to valves, and more particularly, but not by way of limitation, to a valve for placing sensors through vessel walls.
2. Brief Description of Related Art
Electrical power transformers of the size and capacity used by commercial power utilities to maintain primary transmission line voltage are normally charged with a petroleum fluid called insulating or dielectric oil for the dual purpose of insulating the primary and secondary transformer windings, each from the other, and also as a cooling medium to remove inductance heat from the proximity of the transformer core and windings.
Such dielectric oil is also used in relays, switches, oil circuit breakers, and other large capacity power transmission equipment. For brevity, the following description will hereafter be related to transformers, but it will be understood that all such oil insulated transmission devices are included.
In operation, the oil reservoir of such transformers is sealed from the atmosphere. However, if the unit is to be moved from one operating location to another, it is often necessary to remove the oil for weight reduction.
Oil is also removed from a transformer periodically to filter an accumulation of colloidally dispersed carbon particles from the fluid which develop due to localized overheating of the hydrocarbon substance in the course of operation.
It is during these occasions of field removal and recharging that opportunity is given for moisture infusion into the system. The primary objection to moisture in the oil charge is that water concentrations above a very low threshold percentage reduce the dielectric characteristic of the oil (increase the conductance) sufficiently to permit arcing across the windings. Consequently, rapid thermal dissociation of the hydrocarbon compounds occurs to generate catastrophic pressure increases within the sealed transformer housing. Transformer explosion is the terminal result.
Although great care is normally taken during the oil charging and cleaning process, precautionary procedures are, nevertheless, subject to occasional human failure. As a result of such occasional failures and the enormous expense for repair or replacement of the damaged equipment, the consequent economic burden is a significant factor in the operating overhead of utility companies.
Transmission units and other hydraulic systems may also become contaminated with water as a result of working in wet or damp environments. Water will cause an increase in both parts of the oil's complex permittivity.
In addition, the oil may be filtered too soon. Other useful properties in the oil allow the oil to be reused.
To this end, a need exists for a valve that will permit the placement of a sensor, detecting oil quality, through a vessel wall without exposing the oil to the environment. It is to such a valve that the present invention is directed.